Conventionally typical seat belt apparatus comprises: a seat belt for restraining an occupant, a seat belt retractor for winding up the seat belt in such a manner as to allow the seat belt to be withdrawn, a tongue which is slidably supported by the seat belt, and a buckle which can be latched with the tongue, and the seat belt apparatus is adapted to restrain the occupant to a vehicle seat when the tongue is pulled and then latched with the buckle by the occupant.
As the aforementioned seat belt retractor, there is a seat belt retractor comprising a spool onto which the seat belt is wound, and a motor for rotating the spool. The seat belt retractor is employed for satisfying needs such as securely winding up the excessively withdrawn seat belt to fit the occupant's body, winding up the withdrawn seat belt until the seat belt is fully accommodated in an storage portion when nobody wears the seat belt, and not making the occupant feel pressure on his or her chest or the like when the occupant normally wears the seat belt. For example, the seat belt apparatus disclosed in Patent document 1 comprises such a motor of which rotational speed is controlled according to ON/OFF of a buckle switch and ON/OFF of a seat belt wearing signal.
It is an object of the invention disclosed in Patent document 1 to provide a seat belt apparatus which accurately determines an interruption of withdrawal so as to wind up the seat belt even when the seat belt is on the way of being withdrawn, thereby preventing the occupant from feeling some pressure due to unnecessary increase of belt tension and thus improving its marketability. Therefore, the seat belt apparatus has a motor speed control means which actuates the motor when a predetermined state is detected that the seat belt is still not worn a lapse of a certain period of time after the start of withdrawing the seat belt by a belt withdrawal detecting means and a belt wearing detecting means, so as to wind up the seat belt. The motor in operation is stopped when the completion of seat belt winding operation is detected by the belt withdrawal detecting means.
Patent document 1: JP2005-219535A